Flare stacks are gas combustion devices used in the oil refinery, chemical processing, and natural gas procurement industries for burning off flammable gases released during processing and procurement. During processing and procurement, combustible or natural gases can build up and be routed to a pressure release valve. When the pressure reaches a particular limit, or is otherwise opened via manual control, the gas travels through the piping in the stack to a flame located at the flare tip or the pilot light. Upon contact with the open flame, the gas will flare.
The gases that are flared tend to be waste gas, although it is possible that natural gases are flared when they cannot be recaptured and used during the refinery process. Gas flaring is important because it prevents natural and waste gases from escaping into the environment. Allowing these gases to simply escape into the environment risks harming the atmosphere (such as by methane gas, which is a greenhouse gas), or possibly poisoning nearby wildlife (such as by a sulfur-based gas). Flare stacks, therefore, play an important part in the refinery process.